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Anti-Site Reordering in LiFePO<sub>4</sub>: Defect Annihilation on Charge Carrier Injection
Park, Kyu-Young,Park, Inchul,Kim, Hyungsub,Lim, Hee-dae,Hong, Jihyun,Kim, Jongsoon,Kang, Kisuk American Chemical Society 2014 Chemistry of materials Vol.26 No.18
<P>Defects critically affect the properties of materials. Thus, controlling the defect concentration often plays a pivotal role in determining performance. In lithium rechargeable batteries, the operating mechanism is based on ion transport, so large numbers of defects in the electrode crystal can significantly impede Li ion diffusion, leading to decreased electrochemical properties. Here, we introduce a new way to heal defects in crystals by a room-temperature electrochemical annealing process. We show that defects in olivine LiFePO<SUB>4</SUB>, an important cathode material, are significantly reduced by the electrochemical recombination of Li/Fe anti-sites. The healed LiFePO<SUB>4</SUB> recovers its high-power capabilities. The types of defects in LiFePO<SUB>4</SUB> and recombination mechanisms are discussed with the aid of first-principles calculations.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/cmatex/2014/cmatex.2014.26.issue-18/cm502432q/production/images/medium/cm-2014-02432q_0004.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/cm502432q'>ACS Electronic Supporting Info</A></P>
Lithium-excess olivine electrode for lithium rechargeable batteries
Park, Kyu-Young,Park, Inchul,Kim, Hyungsub,Yoon, Gabin,Gwon, Hyeokjo,Cho, Yongbeom,Yun, Young Soo,Kim, Jung-Joon,Lee, Seongsu,Ahn, Docheon,Kim, Yunok,Kim, Haegyeom,Hwang, Insang,Yoon, Won-Sub,Kang, Ki The Royal Society of Chemistry 2016 ENERGY AND ENVIRONMENTAL SCIENCE Vol.9 No.9
<P>Lithium iron phosphate (LFP) has attracted tremendous attention as an electrode material for next-generation lithium-rechargeable battery systems due to the use of low-cost iron and its electrochemical stability. While the lithium diffusion in LFP, the essential property in battery operation, is relatively fast due to the one-dimensional tunnel present in the olivine crystal, the tunnel is inherently vulnerable to the presence of Fe-Li anti-site defects (Fe ions in Li ion sites), if any, that block the lithium diffusion and lead to inferior performance. Herein, we demonstrate that the kinetic issue arising from the Fe-Li defects in LFP can be completely eliminated in lithium-excess olivine LFP. The presence of an excess amount of lithium in the Fe ion sites (Li-Fe) energetically destabilizes the Fe-Li-related defects, resulting in reducing the amount of Fe defects in the tunnel. Moreover, we observe that the spinodal decomposition barrier is notably reduced in lithium-excess olivine LFP. The presence of Li-Fe and the absence of Fe-Li in lithium-excess olivine LFP additionally induce faster kinetics, resulting in an enhanced rate capability and a significantly reduced memory effect. The lithium-excess concept in the electrode crystal brings up unexpected properties for the pristine crystal and offers a novel and interesting approach to enhance the diffusivity and open up additional diffusion paths in solid-state ionic conductors.</P>
A New Water Oxidation Catalyst: Lithium Manganese Pyrophosphate with Tunable Mn Valency
Park, Jimin,Kim, Hyunah,Jin, Kyoungsuk,Lee, Byung Ju,Park, Yong-Sun,Kim, Hyungsub,Park, Inchul,Yang, Ki Dong,Jeong, Hui-Yun,Kim, Jongsoon,Hong, Koo Tak,Jang, Ho Won,Kang, Kisuk,Nam, Ki Tae American Chemical Society 2014 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.136 No.11
<P>The development of a water oxidation catalyst has been a demanding challenge for the realization of overall water-splitting systems. Although intensive studies have explored the role of Mn element in water oxidation catalysis, it has been difficult to understand whether the catalytic capability originates mainly from either the Mn arrangement or the Mn valency. In this study, to decouple these two factors and to investigate the role of Mn valency on catalysis, we selected a new pyrophosphate-based Mn compound (Li<SUB>2</SUB>MnP<SUB>2</SUB>O<SUB>7</SUB>), which has not been utilized for water oxidation catalysis to date, as a model system. Due to the monophasic behavior of Li<SUB>2</SUB>MnP<SUB>2</SUB>O<SUB>7</SUB> with delithiation, the Mn valency of Li<SUB>2-<I>x</I></SUB>MnP<SUB>2</SUB>O<SUB>7</SUB> (<I>x</I> = 0.3, 0.5, 1) can be controlled with negligible change in the crystal framework (e.g., volume change ∼1%). Moreover, inductively coupled plasma mass spectrometry, X-ray photoelectron spectroscopy, ex-situ X-ray absorption near-edge structure, galvanostatic charging–discharging, and cyclic voltammetry analysis indicate that Li<SUB>2-<I>x</I></SUB>MnP<SUB>2</SUB>O<SUB>7</SUB> (<I>x</I> = 0.3, 0.5, 1) exhibits high catalytic stability without additional delithiation or phase transformation. Notably, we observed that, as the averaged oxidation state of Mn in Li<SUB>2-<I>x</I></SUB>MnP<SUB>2</SUB>O<SUB>7</SUB> increases from 2 to 3, the catalytic performance is enhanced in the series Li<SUB>2</SUB>MnP<SUB>2</SUB>O<SUB>7</SUB> < Li<SUB>1.7</SUB>MnP<SUB>2</SUB>O<SUB>7</SUB> < Li<SUB>1.5</SUB>MnP<SUB>2</SUB>O<SUB>7</SUB> < LiMnP<SUB>2</SUB>O<SUB>7</SUB>. Moreover, Li<SUB>2</SUB>MnP<SUB>2</SUB>O<SUB>7</SUB> itself exhibits superior catalytic performance compared with MnO or MnO<SUB>2</SUB>. Our study provides valuable guidelines for developing an efficient Mn-based catalyst under neutral conditions with controlled Mn valency and atomic arrangement.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jacsat/2014/jacsat.2014.136.issue-11/ja410223j/production/images/medium/ja-2013-10223j_0012.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ja410223j'>ACS Electronic Supporting Info</A></P>
황인출(Inchul Hwang),박종희(Jong-Hee Park),이문환(Moon-Hwan Lee),박철순(Cheol-Sun Park) 한국통신학회 2022 한국통신학회 학술대회논문집 Vol.2022 No.2
본 논문은 광대역 고감도 균일 디지털 합성 빔 생성 시험장치대에서 빔 합성 배열 안테나의 단일 안테나 성능 검증을 위하여 야외 시험 방법과 시험결과를 기술하였다. 야외 시험을 위해서 전자파장해 관련 규격(CISPR 16-1-4)의 규정된 야외시험장 구성과 유사하도록 구성했으며, 야외 시험을 통해서 안테나의 패턴을 측정 후 측정한 결과를 전자파 무반사실에서 측정한 결과와 비교하여 야외시험장의 유효성을 확인하였다. 또한, 전자파 무반사실(Semi-anechoic chamber)에서 측정할 수 없는 주파수 대역을 야외 시험으로 측정한 결과와 시뮬레이션 결과와 비교하여 LPDA 단일 안테나의 성능을 확인하였다.
박용운(Yongwoon Park),강윤식(Younsik Kang),백인철(Inchul Hak),박규철(Kyuchul Park),박준성(Junsung Park) 한국자동차공학회 2000 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
Recently, some of the passenger vehicles use the navigation system which have the map on the background with related informations for the driver. Similar system has been used in the combat vehicles to enhance the combat readiness and information sharing for the crews. This research presents the Information Processing and Display System(IPDS) which has been developed for the validation of combat vehicle adaptation. Most of the contents cover the function of the map display with related<br/> information with respect to the operational environment, symbol, navigation and position, and information and data communications.
LiFePO<sub>4</sub> with an alluaudite crystal structure for lithium ion batteries
Kim, Jongsoon,Kim, Hyungsub,Park, Inchul,Park, Young-Uk,Yoo, Jung-Keun,Park, Kyu-Young,Lee, Seongsu,Kang, Kisuk The Royal Society of Chemistry 2013 Energy & environmental science Vol.6 No.3
<P>A novel Na-pillared LiFePO<SUB>4</SUB> with an alluaudite structure is reported and its structure is investigated. The alluaudite-LiFePO<SUB>4</SUB> allowed fast lithium diffusion with stable electrochemical cycling in lithium batteries. ∼0.8 Li<SUP>+</SUP> could be extracted and reinserted reversibly for extended cycles <I>via</I> one-phase reaction in contrast to the well-known two-phase reaction in olivine-LiFePO<SUB>4</SUB>.</P> <P>Graphic Abstract</P><P>The novel alluaudite-LiFePO<SUB>4</SUB> allows fast lithium diffusion with stable electrochemical cycling as a cathode in lithium batteries. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c3ee24393a'> </P>
Anomalous Jahn–Teller behavior in a manganese-based mixed-phosphate cathode for sodium ion batteries
Kim, Hyungsub,Yoon, Gabin,Park, Inchul,Park, Kyu-Young,Lee, Byungju,Kim, Jongsoon,Park, Young-Uk,Jung, Sung-Kyun,Lim, Hee-Dae,Ahn, Docheon,Lee, Seongsu,Kang, Kisuk The Royal Society of Chemistry 2015 ENERGY AND ENVIRONMENTAL SCIENCE Vol.8 No.11
<P>We report a 3.8 V manganese-based mixed-phosphate cathode material for applications in sodium rechargeable batteries; i.e., Na4Mn3(PO4)(2)(P2O7). This material exhibits a largest Mn2+/Mn3+ redox potential of 3.84 V vs. Na+/Na yet reported for a manganese-based cathode, together with the largest energy density of 416 W h kg (1). We describe first-principles calculations and experimental results which show that three-dimensional Na diffusion pathways with low-activation-energy barriers enable the rapid sodium insertion and extraction at various states of charge of the Na4-xMn3(PO4)(2)(P2O7) electrode (where x = 0, 1, 3). Furthermore, we show that the sodium ion mobility in this crystal structure is not decreased by the structural changes induced by Jahn-Teller distortion (Mn3+), in contrast to most manganese-based electrodes, rather it is increased due to distortion, which opens up sodium diffusion channels. This feature stabilizes the material, providing high cycle stability and high power performance for sodium rechargeable batteries. The high voltage, large energy density, cycle stability and the use of low-cost Mn give Na4Mn3(PO4)(2)(P2O7) significant potential for applications as a cathode material for large-scale Na-ion batteries.</P>